It has recently become apparent that the environmental component of cancer is more significant than generally imagined. We propose to test noxious dusts and fibers, which are commonly found in the environment, for their ability to induce putative inflammatory mediators from mouse peritoneal macrophages. These molecules are the enzymes, plasminogen activator and collagenase, and prostaglandins. Several environmentally important materials will be used, with particular emphasis on asbestos. These fibers will be manipulated and physical measurements made to determine what structural and chemical characteristics are important for activity in our in vivo and in vitro test systems. We intend to study cellular control mechanisms for the synthesis of the mediators and hopefully to find drugs which could alleviate the deleterious effects of such fibers and dusts. We hope that our data may aid in the establishment of realistic control methods and standards for asbestos levels and types, as we will be placing emphasis on short asbestos fibers. It is also possible that our assays may be useful for detecting other harmful fibers and dusts in the environment. Because peritoneal mesotheliomas are a common form of mesothelioma in asbestos workers, we believe it relevant to be studying the interaction of asbestos with peritoneal cells.